Maintenance alert system for heavy-duty trucks

ABSTRACT

A real-time maintenance alert system and method for use in a heavy-duty truck having an engine controller with memory are provided. The system includes a sensor operative to indicate an engine condition from the group consisting of: oil filter restriction, air filter restriction, fuel filter restriction, oil level, and coolant reserve tank fluid level. Control logic at the engine controller processes the sensor signal to determine a real-time fault condition, when appropriate.

TECHNICAL FIELD

The present invention relates to a real-time maintenance alert systemfor use in a heavy-duty truck having an engine controller with memory.

BACKGROUND ART

In the control of fuel injection systems, electronic control unitshaving volatile and non-volatile memory, input and output drivercircuitry, and a processor capable of executing a stored instruction setare utilized to control various functions of the engine and itsassociated systems. A particular electronic control unit communicateswith numerous sensors, actuators, and other electronic control unitsnecessary to control various functions, which may include variousaspects of fuel delivery, transmission control, or many others.

In heavy-duty truck applications, in addition to utilizing a highlycomplex engine controller that monitors the engine conditions so thatwhen required, engine protection and engine shutdown logic may beexecuted to prevent possible engine damage, some normal service items ofa truck must be physically inspected by opening the hood to physicallycheck each item, preferably each time the truck is stopped. With theheavy-duty trucking industry becoming more and more competitive,maintenance reduction is becoming significantly more important. As such,it is sometimes undesirably time consuming to tilt the hood andphysically check each normal service item of each truck throughout theday at a trucking bay.

For the foregoing reasons, there is a need for a system that facilitatesthe checking of normal service items of a truck.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide areal-time maintenance alert system for use in a heavy-duty truck thatallows normal service items of a truck to be checked at a glance, ratherthan opening the hood to physically check each item.

In carrying out the above object and other objects and features of thepresent invention, a real-time maintenance alert system for use in aheavy-duty truck having an engine and engine controller with memory isprovided. The system comprises a sensor operative to produce a signalindicative of a least one engine condition from the group consisting: anoil filter restriction condition, a fuel filter restriction condition,an air filter restriction condition, an oil level, and a coolant levelin a coolant reserve tank. The system further comprises control logic atthe engine controller. The control logic is configured to process thesensor signal and to determine a real-time fault condition when theengine condition falls outside of a predetermined acceptable range. Thecontrol logic is further operative to produce an output signal inresponse to the real-time fault condition.

In a preferred embodiment, a display device receives the control logicoutput signal; and, the display device has an indicator operative toalert a user of the real-time fault condition.

Further, in carrying out the present invention, a real-time maintenancealert method for use in a heavy-duty truck having an engine and anengine controller with memory is provided. The method comprisesgenerating a signal with an engine sensor, and processing the signalwith control logic at the engine controller. The signal indicates atleast one engine condition from the group consisting of: an oil filterrestriction condition, a fuel filter restriction condition, an airfilter restriction condition, an oil level, and a coolant level at acoolant reserve tank. The signal is processed to determine a real-timefault condition when the engine condition falls outside of apredetermined acceptable range. The control logic is further operativeto produce an output signal in response to the real-time faultcondition. Preferably, the method further comprises generating an alertsignal on a display device to alert a user of the real-time faultcondition when such condition is present.

Still further, in carrying out the present invention, a display devicefor use with a real-time maintenance alert system for a heavy-duty truckhaving and an engine controller with memory is provided. The displaydevice comprises a housing, an interface, and an indicator device. Theinterface is configured to communicate with control logic at the enginecontroller. The control logic is configured to process a sensor signalindicative of an engine condition from the group consisting: an oilfilter restriction condition, a fuel filter restriction condition, anair-filter restriction condition, an oil level, and a coolant level in acoolant reserve tank. The control logic is further configured todetermine a real-time fault condition when the engine condition fallsoutside of a predetermined acceptable range. The control logic isfurther operative to produce an output signal in response to thereal-time fault condition. The interface receives the output signal.

The indicator device is affixed to the housing and communicates with theinterface. The indicator device produces a visual indication when theoutput signal corresponding to the real-time fault condition is receivedat the interface.

The advantages associated with the embodiments of the present inventionare numerous. For example, embodiments of the present invention allownormal service items of a truck to be checked at a glance rather thanrequiring opening of the hood to physically check each item. Further,preferably, control logic for the real-time maintenance alert systemoperates independently of any existing engine protection or engineshutdown control logic. That is, the maintenance alert system controllogic provides an indication when normal service items requiremaintenance. It is to be appreciated that the maintenance alert systemembodiments of the present invention alert a user of a real-time faultcondition, based on a sensor measurement, as opposed to based on thepassage of time or distance as measured by the odometer since a previousmaintenance operation.

The above object and other objects, features, and advantages of thepresent invention are readily apparent from the following detaileddescription of the best mode for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fuel injection system made inaccordance with the present invention;

FIG. 2 is a functional block diagram illustrating a real-timemaintenance alert system for a heavy-duty truck and associated methodsused by the system;

FIG. 3 is a block diagram illustrating a real-time maintenance alertmethod of the present invention;

FIG. 4 is a display device of the present invention for use in areal-time maintenance alert system;

FIG. 5 is an alternative display device of the present invention for usewith a real-time maintenance alert system.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a system for controlling a heavy duty truck isshown. The system, generally indicated by reference numeral 10, includesan engine 12 having a plurality of cylinders, fed by fuel injectors. Ina preferred embodiment, engine 12 is a compression-ignition internalcombustion engine, such as a four, six, eight, twelve, sixteen ortwenty-four cylinder diesel engine, or a diesel engine having any otherdesired number of cylinders. The fuel injectors are receivingpressurized fuel from a supply connected to one or more high or lowpressure pumps (not shown) as is well known in the art. Alternatively,embodiments of the present invention may employ a plurality of unitpumps (not shown), with each pump supplying fuel to one of theinjectors.

The system 10 may also include various sensors 20 for generating signalsindicative of corresponding operational conditions or parameters ofengine 12, the vehicle transmission (not shown), and other vehicularcomponents. Sensors 20 are in electrical communication with a controller22 via input ports 24. Controller 22 preferably includes amicroprocessor 26 in communication with various computer readablestorage media 28 via data and control bus 30. Computer readable storagemedia 28 may include any of a number of known devices which function asa read-only memory (ROM) 32, random access memory (RAM) 34, keep-alivememory (KAM) 36, and the like. The computer readable storage media maybe implemented by any of a number of known physical devices capable ofstoring data representing instructions executable via a computer such ascontroller 22. Known devices may include, but are not limited to, PROM,EPROM, EEPROM, flash memory, and the like in addition to magnetic,optical, and combination media capable of temporary or permanent datastorage.

Computer readable storage media 28 include various program instructions,software, and control logic to effect control of various systems andsubsystems of the vehicle, such as engine 12, the vehicle transmission,and the like. Controller 22 receives signals from sensors 20 via inputports 24 and generates output signals which may be provided to variousactuators and/or components via output ports 38. Signals may also beprovided to a display device 40 which includes various indicators suchas lights 42 to communicate information relative to maintenance alertsystem operation. Further, display device 40 may be provided with areset switch 44 and a test switch 46.

A data, diagnostics, and programming interface 48 may also beselectively connected to controller 22 via a plug 50 to exchange variousinformation therebetween. Interface 48 may be used to change valueswithin the computer readable storage media 28, such as configurationsettings and control logic.

In accordance with the present invention, in addition to sensors 20which are tied to engine control features, engine protection features,and shutdown logic, engine 12 communicates with a plurality ofadditional sensors 52. In particular, indicators 42 on display device40, in accordance with the present invention, display informationobtained from additional sensors 52 whose outputs are processed atengine controller 22. In accordance with the present invention,additional sensors 52 include at least one of the following sensor: airfilter restriction sensor 54, fuel filter restriction sensor 56, oilfilter restriction sensor 58, oil level sensor 60, and coolantlevel_(—)2 sensor 62. Coolant level_(—)1 sensor 64 is tied to engineprotection control logic and sensors 20, but is shown near coolantlevel_(—)2 sensor 62 to show the interrelation of the two sensors aswill be described along with further description of the sensors insensor group 52 in accordance with the present invention. Of course, itis to be appreciated that in accordance with the present invention,maintenance alert system control logic which utilizes outputs fromsensor group 52 operates independently of normal control logic forengine control, engine protection and engine shutdown control.

In operation of normal engine logic (not including control logicassociated with sensors 54, 56, 58, 60, and 62, controller 22 receivessignals from sensors 20 and 64 and executes control logic embedded inhardware and/or software to control engine 12. In a preferredembodiment, controller 22 is the DDEC controller available from DetroitDiesel Corporation, Detroit, Mich. Various other features of thiscontroller are described in detail in U.S. Pat. Nos. 5,477,827 and5,445,128, the disclosures of which are hereby incorporated by referencein their entirety.

As will be appreciated by one of ordinary skill in the art, the controllogic may be implemented or effected in hardware, software, or acombination of hardware and software. The various functions arepreferably effected by a programmed microprocessor, such as the DDECcontroller, but may include one or more functions implemented bydedicated electric, electronic, or integrated circuits. As will also beappreciated, the control logic may be implemented using any one of anumber of known programming and processing techniques or strategies andis not limited to the order or sequence illustrated here forconvenience. For example, interrupt or event driven processing istypically employed in real-time control applications, such as control ofa vehicle engine or transmission. Likewise, parallel processing ormulti-tasking systems and methods may be used to accomplish the objects,features, and advantages of the present invention. The present inventionis independent of the particular programming language, operating system,or processor used to implement the control logic illustrated.

With reference to FIG. 2, the operation of a maintenance alert system inaccordance with the present invention is illustrated, along with controllogic 70 within engine controller 22 that processes outputs from sensorgroup 52 to provide input signals for display device 40. Air filterrestriction sensor 54, preferably, is mounted on the air intake tubeafter the air cleaner or on the air cleaner and monitors air inletdepression. Sensor 54 is designed to trigger at one of two set pointsbased on air inlet depression and generate a fault code. The fault codeindicates that the air filter is plugged and needs to be replaced. Thatis, a very large pressure drop across the air filter as determined bymeasuring air inlet depression, may be used as a reliable indicator of aclogged air filter that needs replacement. Additional control logic ispreferably built into the engine controller to help prevent false airfilter restriction codes due to wet filters or clogged air intakes dueto snow and ice build-up.

Control logic at engine controller 22 is configured as follows. Thecontrol logic processes the signal from air filter restriction sensor 54to determine an air filter restriction real-time fault condition whenthe air inlet depression falls below a threshold, as indicated at block72 with the expression: vacuum level is less than X. In a preferredembodiment, as shown at block 72, the threshold is a function of enginerpm and particularly, the threshold is a first value (Y) when the enginerpm is less than a predetermined value (Z) and otherwise the thresholdis the second value, X.

Further, in a preferred embodiment, the air filter restriction real-timefault condition is determined in response to the air inlet depressionfalling below the threshold more than one time during a predeterminedtime interval. As indicated at control logic block 74, it is preferredthat a real-time fault condition only be logged when a second occurrenceof a sensor output indicating an air filter restriction occurs between Pand Q engine hours after a first occurrence thereof. Still further, itis preferred that at control logic block 72, the sensor output isfiltered such that vacuum level or inlet depression must fall below thethreshold for a significant amount of time (preferably predetermined),before one of the “less than” conditions can be satisfied. That is, forvacuum level to be considered less than the threshold by control logicblock 74, vacuum level must fall below the threshold for a predeterminedsignificant amount of time. This implementation is preferred to preventaccidental and unnecessary fault logging.

Fuel filter restriction sensor 56 is positioned and configured tomonitor fuel inlet restriction and is preferably configured to measuredepression after the filter. Oil filter restriction sensor 58 isconfigured and positioned to measure differential pressure across theoil filter. Oil filter restriction sensor 58, preferably, is mounted ina special adaptor that is located between the engine oil filter housingand the front oil filter. The sensor measures the pressure differentialbetween the oil filter inlet and outlet. Once this pressure exceeds apreset value or predetermined threshold, the oil filter is deemed to betoo restrictive and the appropriate fault code is generated. There isspecial logic built into the system to compensate for cold oil and toprovide back up warning in the event that the sensor fails. As shown atcontrol logic block 80, a real-time fault may be determined by themaintenance alert system in the event that the differential pressureexceeds a threshold, X, or in the event that the vacuum level (due to afuel filter inlet restriction) falls below a threshold, Y. Further,similar to air filter restriction sensor 54, sensors 56 and 58preferably have outputs that are filtered by the control logic such thata predetermined significant amount of time must pass with differentialpressure greater than X or vacuum level less than Y prior to a faultbeing logged in the system.

Oil level sensor 60, preferably, is mounted in the engine oil pan andwill indicate low oil around the “add” mark on the dip stick, which issometimes in a heavy-duty engine, the four quart low mark. In such anembodiment, the oil level can only be checked with the engine off (zeroengine rpm). Further, in such an embodiment, there is also a wait timeassociated with the oil level sensor because it will take severalminutes for the oil to drain back to the sump after the engine isstopped. After this wait time, if the oil level sensor determines thatthe oil level is low, a fault code is generated. As shown by controllogic block 82, in a preferred embodiment, a fault condition isdetermined when the oil level falls below a threshold, X, and the engineis not running, and the engine has not been running for a predeterminedamount of time or wait time.

Coolant level_(—)2, or maintenance fault coolant level sensor 62,preferably, is mounted in the surge tank and is designed to indicate lowcoolant around the three quart low point, or three quarts below the topof the tank. This will give notice to the operator/mechanic that thecoolant level is lower than normal before the primary coolant levelsensor (coolant level_(—)1 or shutdown coolant level sensor 64) triggersan engine shutdown (if programmed for shutdown). Preferably, the faultcoolant level sensor 62 is configured such that when the sensor is“dry,” the appropriate fault code is generated. Further, a specialmodule may be required to process the electronic signal from the sensorprior to processing by controller 22.

As shown, engine controller 22, as mentioned previously, operatesshutdown logic that may be triggered based on the output of shutdowncoolant level sensor 64, in addition to fault coolant level sensor 62 ofthe present invention providing a signal to engine controller 22 formaintenance system operation. The outputs of the two sensors are showntogether entering control block 84, but it is to be understood and isappreciated by one of ordinary skill in the art that in accordance withthe present invention, the outputs of sensors 54, 56, 58, 60, and 62(FIG. 1) are processed by control logic within controller 22 that isseparate from any engine protection or engine shutdown control logic,and is provided specifically to allow an operator/mechanic to readilysee the condition of various engine items without being required to openthe truck hood.

With continuing reference to FIG. 2, after outputs 52 are processed byvarious logic blocks 72, 74, 80, 82, 84 within engine controller 22,fault codes are generated by control logic block 76 when necessary andare sent to display device 44 by a connection interface 78. As describedabove, in addition to the control logic of the present invention thatimplements a maintenance alert system, additional maintenance controllogic that is not real-time based is preferably also implemented. Ofcourse, it is to be appreciated that the real-time based maintenancealert system of the present invention is advantageous in that normalmaintenance items are monitored in real-time to allow amechanic/operator to check engine item integrity without being requiredto tilt the hood. An example of a non-real-time maintenance controllogic that may optionally be implemented is indicated at a control logicblock 90 and control logic block 92. Control logic block 90 is areal-time clock and a set of engine control module accumulators. Controlblock 92 determines that maintenance is required when a predeterminedamount of time or amount of distance on the odometer has passed since alast maintenance event. For example, an “oil change needed” alert may beproduced after a set amount of mileage has passed on the odometer aftera previous oil change performed at a time that the timer was reset. Thatis, control logic 90 and 92 provide periodic maintenance monitoring asopposed to real-time monitoring.

It is to be appreciated that in accordance with the present invention,display monitor 44 is optional, and receives information by reading thedata link interface 78. In addition, maintenance alert systems of thepresent invention are preferably implemented so as to be supported bycontroller diagnostics (interface 50, FIG. 1) so that the maintenancealert system may optionally drive the check engine light and stop enginelight instead of the monitor. Still further, if desired, device 48(FIG. 1) may be configured to display information as an alternative orin addition to display monitor 44. Still further, device 44 may beconfigured with an additional indicator for alerting an operator ofengine protection faults normally associated with any existingcontroller diagnostics.

With reference FIG. 3, a real-time maintenance alert method for use in aheavy-duty truck having an engine including an engine controller withmemory is generally indicated at 100. In accordance with the method, asignal is generated with an engine sensor at block 102. The signalindicates at least one engine condition from the group consisting of anoil filter restriction condition, a fuel filter restriction condition,an air filter restriction condition, an oil level, and a coolant levelin a coolant reserve tank. As described above, the oil filterrestriction condition is preferably determined by measuring differentialpressure, while the fuel and air filter restriction conditions arepreferably determined by measuring inlet depression. Still further, theoil level is preferably determined with a sensor that provides validoutput when the engine has stopped, and when the engine has not beenrunning for a predetermined amount of time. Further, the fault coolantlevel sensor utilizes maintenance control logic that is separate fromany existing engine protection or shutdown control logic, but preferablyis implemented so as to co-exist with a primary (shutdown) coolant levelsensor such that the fault coolant level sensor of the present inventionprovides an early warning of potentially dangerously low coolantconditions in the near future. At block 104, the signal or signals fromthe sensor output or outputs are processed at the engine controller.Control logic at the engine controller processes the sensor signal todetermine a real-time fault condition when the engine condition fallsoutside of the predetermined acceptable range. For example, theacceptable range may be determined by a signal threshold value, or aplurality of threshold values with the appropriate threshold value beingdetermined based on other engine conditions, such as engine rpm (forexample, control block 72, FIG. 2). At block 106, an alert signal isgenerated as needed on the display monitor, or optionally with the checkengine and stop engine lights depending on the implementation of thepresent invention.

Is to be appreciated that embodiments of the present invention areparticularly useful because maintenance reduction is becomingsignificantly more important in the trucking industry. Maintenance alertsystems of the present invention provide an easy to use informationcenter connected to the engine that can be used to display the current“go/no go” status of the normal service items of a truck at a glancerather than requiring the operator/mechanic to open the hood andphysically check each item. Preferably, the maintenance alert system ismounted in an interior location easily accessible from outside the truckfor mechanics and other service personnel to view.

With reference to FIG. 4, a preferred embodiment for the display deviceis illustrated. Of course, it is to be appreciated that display 110 maytake a variety of different forms, and the following description is of apreferred implementation thereof. As shown, display device 110 has eightindicators that are preferably bicolor light emitting diodes (LEDs) andtwo switches (filter reset and test). As shown, indicator 112 isilluminated when the ECM is asleep (recommending the key be turned on),indicator 114 indicates the condition of the oil filter, indicator 116indicates the condition of the air filter, indicator 118 indicates thecondition of the fuel filter, indicator 120 indicates the condition ofthe oil level, indicator 122 indicates the condition of the coolantlevel, indicator 124 indicates the presence of any engine controllerengine protection fault codes that may be read at the diagnosticsinterface, indicator 126 indicates the presence of any periodic (mileageor time based) maintenance events. Further, a reset switch 128 isprovided to reset display memory of filters and reread each sensor, anda test switch 130 is provided to test the functioning of the lights anddisplay current data. In a preferred construction, display device 110 isapproximately three inches high, five inches wide, and two inches deep.

With reference to FIG. 5, an alternative display 140 is shown. In thealternative, several of the indicators may be omitted, while providing aselected one or more of the indicators and the appropriate correspondingsensors. In the alternative embodiment, an ignition key “on” indicator142, an oil filter condition indicator 144, an oil level conditionindicator 146, and a coolant level condition indicator 148 are provided.Further, preferably, a reset switch 150 and a test switch 152 areprovided.

Although the present invention has been described in sufficient detailabove, the description found hereinafter is provided to explain in greatdetail, a suitable implementation of the maintenance alert system usingthe preferred DDEC controller, of course, it is to be appreciated thatthe suitable implementation description that follows is exemplary onlyand is not intended to limit the broad scope and spirit of theinvention.

In a preferred embodiment, the display device has both read and transmitcapabilities to access diagnostic codes about the normal service itemsfrom the truck's data link preferably adhering to SAE J1708 for hardwareand SAE J1587 for the communications protocol. In addition to the normalservice items, preferred embodiments of the display device also look forextra service indicators (ECM fault codes and periodic maintenancereports). The codes read from the data link are processed and storedwithin the display device to be displayed on an indicator panel display.The display preferably has each monitored item name printed on thedisplay panel with a bicolored indicator next to the name. Theindicator, preferably an LED, is red if the monitored item needsservice, and is green if the item is acceptable and does not needservicing, and is off if the particular sensor is not configured.

Preferably, the display can request a unique message a short time afterkey on which will determine which of the lights and associated hardwareon the display will be used. Thereafter, the display listens passivelyfor a specific fault code associated with the maintenance monitorsensors via the data bus. As the specific fault codes are received, thestored go/no go status for each parameter is updated for later display.When the ignition is not on, but the engine controller is still awake,the engine controller will not be continuously broadcasting data, butwill accept and respond to requests. Just before the engine controlleris powered down, it will again broadcast the fluid levels, faults, andPM data. After the engine controller has powered down, it will notrespond to requests.

The display unit test button, preferably a momentary contact switch,initiates a test sequence. Once the test sequence is initiated, thedisplay will perform a bulb check by turning on all of the indicators togreen for approximately one second, then to red for approximately onesecond. The display will then request the current periodic maintenancedata, then the current information from memory will be used to turn theindicators to their appropriate color for the data. When a test sequenceis initiated with the ignition on, the display has been passivelylistening and will have current data in memory for the sensors, but willstill need updated periodic maintenance information. When the ignitionis not on, but the engine controller is still active, a request must besent to the engine controller for the fluid level as well as theperiodic maintenance data to update the memory before displaying. Whenthe ignition is not on and the engine controller is not active, the datastored in memory will be used for display.

The display unit also preferably has reset capabilities via a resetbutton (preferably a momentary contact switch) to be used after servicehas been performed to any of the filter items being monitored. The resetclears the display memory of retrieved codes for the configured filteritems, thus changing the red indicators to green until new data isreceived and stored. Pressing and holding the reset button for threeseconds or longer preferably initiates the reset sequence. Theindicators will then light with the appropriate color, based on the newinformation as it is received.

In a preferred embodiment, the display device also performs minordiagnostics to inform the operator if the connection to the data linkhas been broken. This will be known if the ignition input is energizedbut no bus activity is seen within two seconds. When this conditionoccurs, the display device will flash all indicators red at roughly 2 Hzwhile the ignition is on until the reset button is pushed, at which timethe display will go blank. If the display device is energized via thetest button before the link connection has been repaired, the indicatorswill again flash red in place of the normal service items status untilthe ten seconds no activity timer has expired. After the display seesdata bus activity, it will avert back to normal operation with thecurrently stored data and normal updates.

The messaging used preferably meets SAE J1587 communications protocol.Knowing this determines the following PART IDENTIFICATIONS (PID):

Data PID Air Filter Restriction 107 Coolant level 111 Fuel FilterRestriction  95 Oil Filter Restriction  99 Oil Level  98 Fault Codes194/192 ECM Sensor configuration ID #66 ECM Reports Data ID #67

The configuration message preferably is an ECM unique message that isone byte in length. This message provides the information stating whichsensors of the Maintenance monitor system are configured in the ECM. Themessage must be requested from the ECM shortly after the ignition hasbeen turned on (approx. 10 seconds) and additionally can be requested atany other time. The oil level is the only sensor this message ismandatory for, but the other four sensors will be included in themessage as well. The message number and format will be:

ECM Unique ID 66

Bits 8-6: Set to 0

Bit 5: Air Filter Restriction Configured

1=Configured

Bit 4: 2^(nd) Coolant Level Sensor Configured

1=Configured

Bit 3: Fuel Filter Restriction Sensor Configured

1=Configured

Bit 2: Oil Filter Restriction Sensor Configured

1=Configured

Bit 1: Oil Level Sensor Configured

1=Configured

To request an ECM Unique ID, send the following message:

X 254 128 0 Y [0 Q]

where:

X is the MID of the requestor,

Y is an ECM Unique ID desired,

Q is another ECM Unique ID if desired,

If ECM Unique ID 66 and 67 was requested, the response would look like:

128 254 Z 66 V 67 W

where:

Z is either the MID of the requester or the MID of the last device onthe system to make an ECM Unique ID request, and V and W are additionaldata.

Normal Operation

Once the maintenance alert system is in the normal operating mode(passive listening), the system monitors fault codes from both theengine ECM and the maintenance sensors. Each fault code received aboutthe maintenance sensors will only effect the status of one LED. The LEDsfor the levels and the filters will only turn red for service if thefluid is low or the filter restriction is high.

In one suitable indicator configuration using LEDs, the LED functioningis as follows:

LED 1, “Ign Key On”

The function of this light is to inform the operator when the display isshowing memory data rather than current data. This LED will use the +5Vsensor supply input wire. The LED will be:

RED—Sensor supply voltage input grounded Memory Data).

OFF—Sensor supply voltage input at +5V (Current Data).

LED 2, “Oil Level”

The oil level LED will be:

RED—Oil Level PID 98 FMI 1 only (Engine Oil Level Low).

GREEN—Oil Level PID 98 received without fault codes for PID 98.

YELLOW (drive both red and green)—Oil Level PID 98 not received eventhough configured.

OFF—Oil level not configured OR fault codes for PID 98 other than FMI 0.

LED 3, “Oil Filter”

The oil filter LED will be:

RED—Oil filter restriction PID 99 FMI 0 only (Primary Oil FilterRestriction High).

GREEN—Oil filter restriction PID 99 received without fault codes for PID99.

OFF—Oil filter restriction not configured OR fault codes for PID 99other than FMI 0.

LED 4, “Coolant Level”

The coolant level LED will be:

RED—Coolant level PID 111 FMI 1 only (Coolant level low).

GREEN—Coolant level PID 111 received without fault codes for PID 111.

OFF—Coolant level not configured OR fault codes for PID 111 other thanFMI 1.

LED 5, “Air Filter”

The air filter restriction LED will be:

RED—Air filter restriction PID 107 FMI 0 only (Air Filter RestrictionHigh).

GREEN—Air filter restriction PID 107 received without fault codes forPID 107.

OF—Air filter restriction not configured OR fault codes for PID 107other than FMI 0.

LED 6, “DDEC Codes” (Protection Faults)

The ECM codes LED is intended to assist service personnel by indicatingthe presence of fault codes in the ECM.

The ECM Codes LED will be:

RED—The presence of any active fault code from MID 128.

YELLOW—The presence of only inactive fault codes from MID 128.

GREEN—No fault codes from MID 128.

LED 7, “Fuel Filter”

The fuel filter restriction LED will be:

RED—Fuel filter restriction PID 95 FMI 0 only (Primary Fuel FilterRestriction High).

GREEN—Fuel filter restriction PID 95 received without fault codes forPID 95.

OFF—Fuel filter restriction not configured OR fault codes for PID 95other than FMI 0.

LED 8, “DDEC Reports—PM” (Periodic Maintenance)

The Data Pages portion of the ECM has three preventative maintenancereminders normally to be accessed through the DDEC Reports Softwarepackage. An ECM unique message will be used and can be requested to showthe configuration/status of the PM reminders. This message will be onebyte in length with the capability of showing the status of four PMreminders (possibly future ECM expansion) and needs to be requested ateach test sequence, but use the data from memory if the ECM is notpowered.

The message identifier and format will be:

ECM Unique ID 67

Bits 8, 7: Not Defined—Set to 11 (Not Configured)

Bits 6, 5: PM C

00-Configured, No Service Needed

01-Configured, Service Needed

11-Not Configured

Bits 4, 3: PM B

00-Configured, No Service Needed

01-Configured, Service Needed

11-Not Configured

Bits 2, 1: PM A

00-Configured, No Service Needed

01-Configured, Service Needed

11-Not Configured

The DDEC Reports LED will be:

RED—Any one or more of the PM reminders is configured and needs service.

GREEN—None of the configured PM reminders need service.

OFF—None of the PM reminders are configured.

Preferably, the display unit is mounted inside the truck cab on thefloor beside the driver's seat for easy viewing and access whilestanding outside the truck with the driver's door open. The case of thedisplay should then have easy mounting to the floor either directly orvia a suitable bracket thus making for easy viewing conditions whilestanding just outside the door. This mounting location also necessitatesthat the case be made of a reasonably sturdy material to prevent damageif bumped with a hammer, fire extinguisher, etc. The display should besealed for the occasional cleaning of the cab via water hose and a havea −40 to 85 degree Celsius temperature range. The products usedpreferably also are built to withstand the normal cleaning fluids andother materials found inside a truck just as the main instrument panelmust.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A real-time maintenance alert system for use in aheavy duty truck having an engine including an air filter at an airinlet, and an engine controller having a communications data link and,the system comprising: a sensor operative to produce a signal indicativeof an air inlet depression; control logic at the engine controller, thecontrol logic being conjured to process the sensor signal and todetermine an air filter restriction real-time fault condition when theair inlet depression falls below a threshold, the control logic beingoperative to produce an output signal at the data link in response tothe air filter restriction real-time fault condition; and a displaydevice having a memory and configured to transmit and receiveinformation over the data link, the display device processing the outputsignal and storing a status of the air filter in the memory, andgenerating an output signal indicative of the status.
 2. The system ofclaim 1 wherein the threshold is a function of an engine rpm.
 3. Thesystem of claim 2 wherein the threshold is a first value when the enginerpm is less than a predetermined value and, otherwise, the threshold isa second value.
 4. The system of claim 1 wherein the air filterrestriction real-time fault condition is determined in response to theair inlet depression falling below the threshold more than one timeduring a predetermined time interval.
 5. A real-time maintenance alertsystem for use in a heavy duty truck having an engine including a fuelfilter at a fuel inlet, and an engine controller having a communicationsdata link and, the system comprising: a sensor operative to produce asignal indicative of a fuel inlet depression; control logic at theengine controller, the control logic being configured to process thesensor signal and to determine a fuel filter restriction real-time faultcondition when the fuel inlet depression falls below a threshold, thecontrol logic being operative to produce an output signal at the datalink in response to the fuel filter restriction real-time faultcondition; and a display device having a memory and configured totransmit and receive information over the data link, the display deviceprocessing the output signal and storing a status of the fuel filter inthe memory, and generating an output signal indicative of the status. 6.A real-time maintenance alert system for use in a heavy duty truckhaving an engine including an oil filter having an inlet and an outlet,and an engine controller having a communications data link and, thesystem comprising: a sensor operative to produce a signal indicative ofan oil filter pressure differential between the oil filter inlet and theoil filter outlet; control logic at the engine controller, the controllogic being configured to process the sensor signal and to determine anoil filter restriction real-time fault condition when the oil filterpressure differential exceeds a threshold, the control logic beingoperative to produce an output signal at the data link in response tothe oil filter restriction real-time fault condition; and a displaydevice having a memory and configured to transmit and receiveinformation over the data link, the display device processing the outputsignal and storing a status of the oil filter in the memory, andgenerating an output signal indicative of the status.
 7. A real-timemaintenance alert system for use in a heavy duty truck having an engineincluding an oil pan, and an engine controller having a communicationsdata link and, the system comprising: a sensor operative to produce asignal indicative of an oil level; control logic at the enginecontroller, the control logic being configured to process the sensorsignal and to determine a low oil real-time fault condition when the oillevel falls below a threshold, the control logic being operative toproduce an output signal at the data link in response to the oil levelreal-time fault condition; and a display device having a memory andconfigured to transmit and receive information over the data link, thedisplay device processing the output signal and storing a status of theoil level in the memory, and generating an output signal indicative ofthe status.
 8. The system of claim 7 wherein the low oil real-time faultcondition is determined in response to the oil level falling below thethreshold while the engine is not running.
 9. The system of claim 8wherein the low oil real-time fault condition is determined in responseto the oil level being below the threshold while the engine is notrunning and has not been running for a predetermined time interval. 10.A real-time maintenance alert system for use in a heavy duty truckhaving an engine including a coolant reserve tank, and an enginecontroller having a communications data link and, the system comprising:a sensor operative to produce a signal indicative of a coolant level;control logic at the engine controller, the control logic beingconfigured to process the sensor signal and to determine a low coolantreal-time fault condition when the coolant level falls below athreshold, the control logic being operative to produce an output signalat the data link in response to the low coolant real-time faultcondition, wherein the threshold is sufficiently high such that engineshutdown is not required upon the presence of the low coolant real-timefault condition; and a display device having a memory and configured totransmit and receive information over the data link, the display deviceprocessing the output signal and storing a status of the coolant reservetank in the memory, and generating an output signal indicative of thestatus.
 11. The system of claim 10 further comprising: a primary coolantlevel sensor operative to produce a signal indicative of a sufficientlylow coolant level to demand engine shutdown, wherein the control logicis further configured to determine an engine shutdown fault upon thepresence of the primary coolant level sensor signal.
 12. A real-timemaintenance alert system for use in a heavy duty truck having an engine,and an engine controller having a communications data link, the systemcomprising: a sensor operative to produce a signal indicative of atleast one engine condition from the group consisting of: an oil filterrestriction condition, a fuel filter restriction condition, an airfilter restriction condition, an oil level, and a coolant level in acoolant reserve tank; control logic at the engine controller, thecontrol logic being configured to process the sensor signal and todetermine a real-time fault condition when the engine condition fallsoutside of a predetermined acceptable range, the control logic beingoperative to produce an output signal at the data link in response tothe real-time fault condition; and a display device having memory andconfigured to transmit and receive information over the data link, thedisplay device processing the output signal and storing a faultcondition status in the memory, the display device having an indicatoroperative to alert a user of the real-time fault condition.
 13. Areal-time maintenance alert method for use in a heavy duty truck havingan engine, and an engine controller having a communications data linkand, the method comprising: generating a signal with an engine sensor,the signal being indicative of at least one engine condition from thegroup consisting of: an oil filter restriction condition, a fuel filterrestriction condition, an air filter restriction condition, an oillevel, and a coolant level in a coolant reserve tank; processing thesignal with control logic at the engine controller to determine areal-time fault condition when the engine condition falls outside of apredetermined acceptable range, the control logic being operative toproduce an output signal at the data link in response to the real-timefault condition; receiving the output signal over the data link at adisplay device having a memory; and storing a fault condition status inthe memory.
 14. The method of claim 13 further comprising: generating analert signal on the display device to alert a user of the real-timefault condition.
 15. A display device for use with a real-timemaintenance alert system for a heavy duty truck having an engine and anengine controller having a communications data link, the display devicecomprising: a housing; an interface configured to communicate withcontrol logic at the engine controller over the data link, the controllogic being configured to process a sensor signal indicative of anengine condition from the group consisting of: an oil filter restrictioncondition, a fuel filter restriction condition, an air filterrestriction condition, an oil level, and a coolant level in a coolantreserve tank, and the control logic being further configured todetermine a real-time fault condition when the engine condition fallsoutside of a predetermined acceptable range, the control logic beingoperative to produce an output signal at the data link in response tothe real-time fault condition, the interface receiving the outputsignal; a memory for storing a fault condition status based on theoutput signal; and an indicator device affixed to the housing and incommunication with the interface, the indicator device producing avisual indication when the output signal corresponding to the real-timefault condition is received at the interface.
 16. The display device ofclaim 15 wherein the control logic is further configured with engineprotection shutdown logic operative to provide an engine protectionfault condition signal to the interface, the display device furthercomprising: an engine protection indicator device affixed to the housingand in communication with the interface, the engine protection indicatordevice producing a visual indication when the output signalcorresponding to the engine protection fault condition is received atthe interface.
 17. The display device of claim 15 wherein the controllogic is further configured with periodic maintenance logic operative toprovide a periodic maintenance fault condition signal to the interface,the display device further comprising: a periodic maintenance indicatordevice affixed to the housing and in communication with the interface,the periodic maintenance indicator device producing a visual indicationwhen the output signal corresponding to the periodic maintenance faultcondition is received at the interface.
 18. The display device of claim15 further comprising: a reset switch in communication with theinterface, wherein the interface and the control logic are configuredsuch that assertion of the reset switch causes a refreshing of thesensor signal.
 19. The display device of claim 15 further comprising: atest switch in communication with the indicator device, wherein theindicator device is configured to produce the visual indication for apredetermined period of time in response to assertion of the testswitch.
 20. The display device of claim 15 wherein the indicator devicecomprises: a light emitting diode.